MPLS label

As explained in Acing the CCNA Exam: Volume 2 Advanced Networking and Security

An MPLS label is a fixed-length header value inserted into a packet to identify a predetermined forwarding path through an MPLS network.

An MPLS label is a fixed-length additional header inserted between the Layer 2 and Layer 3 headers. Routers use it instead of repeatedly examining the entire IP header and consulting routing tables, forwarding packets along a predetermined path. MPLS networks commonly carry IPv4 or IPv6 traffic, but can encapsulate other packet types as well. section 16.1.2

Figure 16.3 The MPLS label is inserted between the Layer 2 and Layer 3 headers.

Shows the label’s position between the Layer 2 and Layer 3 headers, clarifying why MPLS is often called a Layer 2.5 protocol. section 16.1.2

Understand the label’s operational context through the routers that process it:

• PE routers add labels to customer packets and remove them at the provider-network edge. section 16.1.2
• P routers operate inside the provider network and forward labeled packets without directly connecting to customers. section 16.1.2
• Labels support shared provider infrastructure by segregating customer traffic through MPLS VPNs, including L2VPN and L3VPN services. section 16.4

How Acing the CCNA Exam: Volume 2 Advanced Networking and Security covers it

How deep it goes

Defines placement, forwarding purpose, and router roles, but does not detail label fields, commands, or configuration procedures.

Examples

Uses a header-placement figure and shared customer WAN scenarios to illustrate label insertion and traffic segregation.

What it assumes

Assumes basic IP forwarding knowledge while defining label placement, MPLS roles, and shared-network behavior.

What you can do after

Evaluate how MPLS labels reduce forwarding work and distinguish PE and P router responsibilities.

How it connects

Connects Layer 2, Layer 3, IP routing, PE routers, P routers, CE routers, and MPLS VPN services.

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Related concepts

• Multiprotocol Label Switchingused by · Multiprotocol Label Switching is a packet-forwarding technology that directs traffic using short labels associated with packets rather than repeatedly evaluating network-layer addresses.
• provider edge routerused by · A provider edge router is an MPLS router at the edge of a service provider network that connects to customer networks and manages MPLS labels for customer traffic.

This explainer was generated by Manning's knowledge graph from the text of Acing the CCNA Exam: Volume 2 Advanced Networking and Security. The section links point to the parts of the book it draws on.